Metro Interim General Manager Dan Tangherlini is withdrawing as a candidate to head the transit authority permanently after agreeing to become the District's city administrator if Adrian M. Fenty is elected mayor.

Tangherlini's decision would fill a key position in Fenty's administration but deprive Metro of the candidate several Metro board members favored when they took a preliminary vote several months ago.

Tangherlini, 39, was on the short list of candidates that Metro's board was to interview this week in its search for a permanent chief executive of a system that provides the nation's second-busiest subway and fifth-busiest bus service.

But Tangherlini, who spent six years as the head of the District's transportation department until joining Metro this year, agreed to join Fenty, a Democrat, if he wins the Nov. 7 general election in the heavily Democratic city.

"I was impressed by what he wanted to do and excited about the role he wanted me to play," Tangherlini said. "It's a once in a lifetime opportunity to make a difference in this city I call my home town."

Fenty, who is to make a formal announcement at a news conference today, said Tangherlini stood out among D.C. government agency chiefs for his responsiveness. In an interview yesterday, Fenty hailed Tangherlini as an "exceptional manager."

"Dan Tangherlini is a new type of manager . . . who could easily succeed in the private sector but who understands and loves public service and is willing to commit to that," said Fenty, who represents Ward 4 on the D.C. Council. "He definitely stood out for responsiveness and preparation, sound management, holding people accountable, encouraging people to do more, hiring a competent staff."

Fenty, who announced two weeks ago that he would nominate D.C. Chief Financial Officer Natwar M. Gandhi for another five-year term, is moving quickly to establish his cabinet well before the general election. He said he offered Tangherlini the job of city administrator now to lure him before Metro interviewed him, even giving Tangherlini a written promise.

Tangherlini, a Capitol Hill resident, pulled out from consideration for the Metro job now because he didn't want to "send the wrong signal," he said. "I wanted the search to be legitimate and for the board to be able to make a selection for the best candidate."

If Fenty wins, he can't make formal appointments until January. But Fenty said he hopes Tangherlini would join his team during the two-month transition after the general election. The two men have talked about the timing but need to work out the details with the Metro board as to when Tangherlini would be able to leave. His contract runs through mid-February.

Tangherlini said he plans to deliver a letter to Metro board members today informing them that he is withdrawing from the search.